Question 1

What is ΔH°rxn for the following reaction? SiO2(s)  + 4HCl(g)  → SiCl4(g)  + 2H2O(g)  rxn for the following reaction? SiO2(s)  + 4HCl(g)  → SiCl4(g)  + 2H2O(g)    A)  -1856.2 kJ/mol B)  -1372.6 kJ/mol C)  -47.0 kJ/mol D)  82.1 kJ/mol E)  530.6 kJ/mol" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   -1856.2 kJ/mol
B)   -1372.6 kJ/mol
C)   -47.0 kJ/mol
D)   82.1 kJ/mol
E)   530.6 kJ/molF) A) and C)
G) C) and D)

Question 2

Given the following ΔH° values
H2(g) + ½O2(g) → H2O(l) ΔH°f = -285.8 kJ
H2O2(l) → H2(g) + O2(g) ΔH°rxn = 187.6 kJ
calculate ΔH°rxn for the reaction H2O2(l) → H2O(l) + ½O2(g),

Accepted Answer

Question 3

A system receives 575 J of heat and delivers 424 J of work. What is the change in the internal energy, ΔU, of the system?

Accepted Answer

A)   -150. J
B)   150. J
C)   -1000. J
D)   1000. J
E)   575 JF) C) and E)
G) A) and B)

Question 4

What is ΔH°rxn for the following reaction? H3AsO4(aq)  + 4H2(g)  → AsH3(g)  + 4H2O(l)  rxn for the following reaction? H3AsO4(aq)  + 4H2(g)  → AsH3(g)  + 4H2O(l)    A)  -1876.3 kJ/mol B)  -1018.9 kJ/mol C)  -790.3 kJ/mol D)  -410.1 kJ/mol E)  -67.1 kJ/mol" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   -1876.3 kJ/mol
B)   -1018.9 kJ/mol
C)   -790.3 kJ/mol
D)   -410.1 kJ/mol
E)   -67.1 kJ/molF) A) and E)
G) A) and D)

Question 5

An ideal gas (the system)  is contained in a flexible balloon at a pressure of 1 atm and is initially at a temperature of 20.°C. The surrounding air is at the same pressure, but its temperature is 25°C. When the system has equilibrated with its surroundings, both system and surroundings are at 25°C and 1 atm. In changing from the initial to the final state, which one of the following relationships regarding the system is correct?

Accepted Answer

A)   ΔU 
B)   ΔU = 0
C)   ΔH = 0
D)   w > 0
E)   q > 0F) A) and E)
G) A) and C)

Question 6

A system which does work on the surroundings with no heat change has

Accepted Answer

A)   w = ΔU.
B)   w = -ΔU.
C)   w > 0, ΔU 
D)   w  0.
E)   w > ΔU.F) A) and B)
G) C) and E)

Question 7

How much heat is required to raise the temperature of 1500 g of water from 25°C to 52°C? The specific heat of water is 4.184 J/g·°C.

Accepted Answer

A)   1500 kJ
B)   170 kJ
C)   6.3 kJ
D)   41 J
E)   41 kJF) A) and B)
G) None of the above

Question 8

Using Hess' law, what is ΔH°rxn at 25°C for the following reaction? ClF(g)  + F2(g)  → ClF3(g)  rxn at 25°C for the following reaction? ClF(g)  + F2(g)  → ClF3(g)    A)  -217.5 kJ/mol B)  -130.2 kJ/mol C)  217.5 kJ/mol D)  -108.7 kJ/mol E)  465.4 kJ/mol" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   -217.5 kJ/mol
B)   -130.2 kJ/mol
C)   217.5 kJ/mol
D)   -108.7 kJ/mol
E)   465.4 kJ/molF) B) and C)
G) C) and D)

Question 9

Solid sodium peroxide (Na2O2)  reacts with liquid water yielding aqueous sodium hydroxide and oxygen gas. How much heat is released if 327.2 g of oxygen gas is produced from the reaction of sodium peroxide and water under standard-state conditions? 2O2)  reacts with liquid water yielding aqueous sodium hydroxide and oxygen gas. How much heat is released if 327.2 g of oxygen gas is produced from the reaction of sodium peroxide and water under standard-state conditions?   A)  46,630 kJ B)  1457 kJ C)  6689 kJ D)  3345 kJ E)  2914 kJ" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   46,630 kJ
B)   1457 kJ
C)   6689 kJ
D)   3345 kJ
E)   2914 kJF) A) and D)
G) A) and B)

Question 10

In an endothermic reaction, in going from the reactants to the products at the same temperature, the value of q is negative.

Accepted Answer

A) True 
 B)False

Question 11

What is the equation for the formation reaction for gaseous hydrazine, N2H4, at 25ºC and 1 atm pressure?

Accepted Answer

A)   2N2H4(g)  → 2NH3(g)  + H2(g) 
B)   2NH3(g)  + H2(g)  → N2H4(g) 
C)   N2(g)  + 2H2O(g)  → N2H4 (g)  + O2(g) 
D)   N2(g)  +2H2(g)  → N2H4(g) 
E)   2NO2(g)  + 6H2(g)  → N2H4(g)  + 4H2O(g) F) A) and B)
G) B) and D)

Question 12

What is ΔH°rxn for the reaction 2Al2O3(s)  → 4Al(s)  + 3O2(g) ? ΔH°f(Al2O3(s) )  = -1670 kJ/mol

Accepted Answer

A)   3340 kJ/mol
B)   1670 kJ/mol
C)   -3340 kJ/mol
D)   -1670 kJ/mol
E)   -835 kJ/molF) A) and B)
G) C) and E)

Question 13

A 100.-g sample of Cu is heated to 400.oC and then plunged into 1000. g of water at 22.6oC. What is the final temperature? Specific heat capacity: Cu: 0.385 J/g·°C;water: 4.184 J/g·°C

Accepted Answer

Question 14

Using Hess's law, what is ΔH°rxn for the following reaction? WO3(s)  + 3H2(g)  → W(s)  + 3H2O(g)  rxn for the following reaction? WO3(s)  + 3H2(g)  → W(s)  + 3H2O(g)    A)  117.5 kJ/mol B)  235.0 kJ/mol C)  359.3 kJ/mol D)  1202.2 kJ/mol E)  2169.4 kJ/mol" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   117.5 kJ/mol
B)   235.0 kJ/mol
C)   359.3 kJ/mol
D)   1202.2 kJ/mol
E)   2169.4 kJ/molF) A) and E)
G) C) and E)

Question 15

How much heat is evolved if 0.600 kg of SO2 is burned in excess oxygen? 2SO2(g)  + O2(g)  → 2SO3(g)  ΔH°rxn= -198 kJ/mol

Accepted Answer

A)   5.46 × 10-2 kJ
B)   927 kJ
C)   1.85 × 103 kJ
D)   59,400 kJ
E)   3.71 × 103 kJF) A) and E)
G) A) and C)

Question 16

The heat absorbed by a system at constant pressure is equal to ΔU + PΔV.

Accepted Answer

A) True 
 B)False

Question 17

For the reaction: 2A + B2 → 2AB ΔH = +50.0 kJ.

Accepted Answer

A)   The reaction is endothermic.
B)   Heat is released to the surroundings.
C)   The standard enthalpy of formation for AB is 50.0 kJ.
D)   The bond energy for each A-B bond is 50.0 kJ.
E)   The molecule AB contains less energy than A or B2.F) A) and B)
G) A) and C)

Question 18

Which equation has a ΔHrxn that is not equal to ΔHof of the product?

Accepted Answer

A)   O2(g)  + H2(g)  → H2O2(g) 
B)   ½O2(g)  + H2(g)  → H2O(g) 
C)   H2(g)  + ½O2(g)  + → H2O(l) 
D)   NO(g)  + ½O2(g)  → NO2(l) 
E)   ½H2(g)  + ½Cl2(g)  → HCl(g) F) B) and C)
G) A) and E)

Question 19

In which reaction would you expect ΔH to be substantially greater than ΔU (i.e., ΔH > ΔU) ?

Accepted Answer

A)   H2(g)  + Br2(g)  → 2HBr(g) 
B)   CO2(s)  → CO2(g) 
C)   C2H2(g)  + H2(g)  → C2H4(g) 
D)   H2O(s)  → H2O(l) 
E)   HCl(aq)  + NaOH(aq)  → NaCl(aq)  + H2O(l) F) C) and E)
G) A) and C)

Question 20

Pentaborane B5H9(s)  burns vigorously in O2 to give B2O3(s)  and H2O(l) . What is ΔH° for the combustion of 1 mol of B5H9(s) ? Substance ΔH°f (kJ/mol) 
B2O3(s)  -1273.5
B5H9(s)  +73.2
H2O(l)  -285.8

Accepted Answer

A)   -1486.1 kJ
B)   -1632.5 kJ
C)   -4396.7 kJ
D)   -4652.85 kJ
E)   -9086.1 kJF) A) and D)
G) A) and E)

Exam 5: Thermochemistry

Given the following ΔH° values H₂(g) + ½O₂(g) → H₂O(l) ΔH°_f = -285.8 kJ H₂O₂(l) → H₂(g) + O₂(g) ΔH°_rxn = 187.6 kJ calculate ΔH°_rxn for the reaction H₂O₂(l) → H₂O(l) + ½O₂(g),

Correct Answer
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Using Hess' law, what is ΔH°_rxnat 25°C for the following reaction? ClF(g) + F₂(g) → ClF₃(g)

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Which equation has a ΔH_rxn that is not equal to ΔH^o_f of the product?

Correct Answer
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The heat absorbed by a system at constant pressure is equal to ΔU + PΔV.

Correct Answer
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In an endothermic reaction, in going from the reactants to the products at the same temperature, the value of q is negative.

Correct Answer
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Solid sodium peroxide (Na₂O₂) reacts with liquid water yielding aqueous sodium hydroxide and oxygen gas. How much heat is released if 327.2 g of oxygen gas is produced from the reaction of sodium peroxide and water under standard-state conditions?

Correct Answer
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How much heat is evolved if 0.600 kg of SO₂ is burned in excess oxygen? 2SO₂(g) + O₂(g) → 2SO₃(g) ΔH°_rxn= -198 kJ/mol

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Pentaborane B₅H₉(s) burns vigorously in O₂ to give B₂O₃(s) and H₂O(l) . What is ΔH° for the combustion of 1 mol of B₅H₉(s) ? Substance ΔH°_f (kJ/mol) B₂O₃(s) -1273.5 B₅H₉(s) +73.2 H₂O(l) -285.8

Correct Answer
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A system receives 575 J of heat and delivers 424 J of work. What is the change in the internal energy, ΔU, of the system?

Correct Answer
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How much heat is required to raise the temperature of 1500 g of water from 25°C to 52°C? The specific heat of water is 4.184 J/g·°C.

Correct Answer
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A 100.-g sample of Cu is heated to 400.^oC and then plunged into 1000. g of water at 22.6^oC. What is the final temperature? Specific heat capacity: Cu: 0.385 J/g·°C;water: 4.184 J/g·°C

Correct Answer
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What is ΔH°_rxn for the reaction 2Al₂O₃(s) → 4Al(s) + 3O₂(g) ? ΔH°_f(Al₂O₃(s) ) = -1670 kJ/mol

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Using Hess's law, what is ΔH°_rxn for the following reaction? WO₃(s) + 3H₂(g) → W(s) + 3H₂O(g)

Correct Answer
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For the reaction: 2A + B₂→ 2AB ΔH = +50.0 kJ.

Correct Answer
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What is the equation for the formation reaction for gaseous hydrazine, N₂H₄, at 25ºC and 1 atm pressure?

Correct Answer
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In which reaction would you expect ΔH to be substantially greater than ΔU (i.e., ΔH > ΔU) ?

Correct Answer
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What is ΔH°_rxn for the following reaction? H₃AsO₄(aq) + 4H₂(g) → AsH₃(g) + 4H₂O(l)

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What is ΔH°_rxn for the following reaction? SiO₂(s) + 4HCl(g) → SiCl₄(g) + 2H₂O(g)

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A system which does work on the surroundings with no heat change has

Correct Answer
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Exam 5: Thermochemistry

Given the following ΔH° values H2(g) + ½O2(g) → H2O(l) ΔH°f = -285.8 kJ H2O2(l) → H2(g) + O2(g) ΔH°rxn = 187.6 kJ calculate ΔH°rxn for the reaction H2O2(l) → H2O(l) + ½O2(g),

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Using Hess' law, what is ΔH°rxn at 25°C for the following reaction? ClF(g) + F2(g) → ClF3(g)

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Which equation has a ΔHrxn that is not equal to ΔHof of the product?

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The heat absorbed by a system at constant pressure is equal to ΔU + PΔV.

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In an endothermic reaction, in going from the reactants to the products at the same temperature, the value of q is negative.

Correct AnswerverifiedShow Answer

Solid sodium peroxide (Na2O2) reacts with liquid water yielding aqueous sodium hydroxide and oxygen gas. How much heat is released if 327.2 g of oxygen gas is produced from the reaction of sodium peroxide and water under standard-state conditions?

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How much heat is evolved if 0.600 kg of SO2 is burned in excess oxygen? 2SO2(g) + O2(g) → 2SO3(g) ΔH°rxn= -198 kJ/mol

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Pentaborane B5H9(s) burns vigorously in O2 to give B2O3(s) and H2O(l) . What is ΔH° for the combustion of 1 mol of B5H9(s) ? Substance ΔH°f (kJ/mol) B2O3(s) -1273.5 B5H9(s) +73.2 H2O(l) -285.8

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A system receives 575 J of heat and delivers 424 J of work. What is the change in the internal energy, ΔU, of the system?

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How much heat is required to raise the temperature of 1500 g of water from 25°C to 52°C? The specific heat of water is 4.184 J/g·°C.

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A 100.-g sample of Cu is heated to 400.oC and then plunged into 1000. g of water at 22.6oC. What is the final temperature? Specific heat capacity: Cu: 0.385 J/g·°C;water: 4.184 J/g·°C

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What is ΔH°rxn for the reaction 2Al2O3(s) → 4Al(s) + 3O2(g) ? ΔH°f(Al2O3(s) ) = -1670 kJ/mol

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Using Hess's law, what is ΔH°rxn for the following reaction? WO3(s) + 3H2(g) → W(s) + 3H2O(g)

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For the reaction: 2A + B2 → 2AB ΔH = +50.0 kJ.

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What is the equation for the formation reaction for gaseous hydrazine, N2H4, at 25ºC and 1 atm pressure?

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In which reaction would you expect ΔH to be substantially greater than ΔU (i.e., ΔH > ΔU) ?

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What is ΔH°rxn for the following reaction? H3AsO4(aq) + 4H2(g) → AsH3(g) + 4H2O(l)

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What is ΔH°rxn for the following reaction? SiO2(s) + 4HCl(g) → SiCl4(g) + 2H2O(g)

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A system which does work on the surroundings with no heat change has

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Given the following ΔH° values H₂(g) + ½O₂(g) → H₂O(l) ΔH°_f = -285.8 kJ H₂O₂(l) → H₂(g) + O₂(g) ΔH°_rxn = 187.6 kJ calculate ΔH°_rxn for the reaction H₂O₂(l) → H₂O(l) + ½O₂(g),

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Using Hess' law, what is ΔH°_rxnat 25°C for the following reaction? ClF(g) + F₂(g) → ClF₃(g)

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Which equation has a ΔH_rxn that is not equal to ΔH^o_f of the product?

Correct Answer
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Correct Answer
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Solid sodium peroxide (Na₂O₂) reacts with liquid water yielding aqueous sodium hydroxide and oxygen gas. How much heat is released if 327.2 g of oxygen gas is produced from the reaction of sodium peroxide and water under standard-state conditions?

Correct Answer
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How much heat is evolved if 0.600 kg of SO₂ is burned in excess oxygen? 2SO₂(g) + O₂(g) → 2SO₃(g) ΔH°_rxn= -198 kJ/mol

Correct Answer
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Pentaborane B₅H₉(s) burns vigorously in O₂ to give B₂O₃(s) and H₂O(l) . What is ΔH° for the combustion of 1 mol of B₅H₉(s) ? Substance ΔH°_f (kJ/mol) B₂O₃(s) -1273.5 B₅H₉(s) +73.2 H₂O(l) -285.8

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A 100.-g sample of Cu is heated to 400.^oC and then plunged into 1000. g of water at 22.6^oC. What is the final temperature? Specific heat capacity: Cu: 0.385 J/g·°C;water: 4.184 J/g·°C

Correct Answer
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What is ΔH°_rxn for the reaction 2Al₂O₃(s) → 4Al(s) + 3O₂(g) ? ΔH°_f(Al₂O₃(s) ) = -1670 kJ/mol

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Using Hess's law, what is ΔH°_rxn for the following reaction? WO₃(s) + 3H₂(g) → W(s) + 3H₂O(g)

Correct Answer
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For the reaction: 2A + B₂→ 2AB ΔH = +50.0 kJ.

Correct Answer
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What is the equation for the formation reaction for gaseous hydrazine, N₂H₄, at 25ºC and 1 atm pressure?

Correct Answer
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Correct Answer
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What is ΔH°_rxn for the following reaction? H₃AsO₄(aq) + 4H₂(g) → AsH₃(g) + 4H₂O(l)

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What is ΔH°_rxn for the following reaction? SiO₂(s) + 4HCl(g) → SiCl₄(g) + 2H₂O(g)

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Correct Answer
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